The National Football League and its players’ union on Saturday angrily denounced President Donald Trump for suggesting that owners fire players who kneel during the national anthem and that fans consider walking out in protest “when somebody disrespects our flag.”

“Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game and all of our players,” the league commissioner, Roger Goodell, said in a statement.

DeMaurice Smith, executive director of the NFL Players Association, tweeted: “We will never back down. We no longer can afford to stick to sports.”

Trump, during a political rally in Alabama on Friday night, also blamed a drop in NFL ratings on the nation’s interest in “yours truly” as well as what he contended was a decline in violence in the game.

Smith said the union won’t shy away from “protecting the constitutional rights of our players as citizens as well as their safety as men who compete in a game that exposes them to great risks.”

Trump kept up his foray into the sports world today, when he responded to comments by Stephen Curry of the Golden State Warriors, who has made it clear that he’s not interested in a traditional White House trip for the NBA champions

“Going to the White House is considered a great honor for a championship team. Stephen Curry is hesitating, therefore invitation is withdrawn!” Trump tweeted while spending the weekend at his golf club in New Jersey.

It was not immediately clear whether Trump was rescinding the invitation for Curry or the entire team.

Several athletes, including a handful of NFL players, have refused to stand during “The Star-Spangled Banner” to protest of the treatment of blacks by police. Quarterback Colin Kaepernick, who started the trend last year when he played for the San Francisco 49ers, hasn’t been signed by an NFL team for this season.

Trump, who once owned the New Jersey Generals of the U.S. Football League, said those players are disrespecting the American flag and deserve to lose their jobs.

“That’s a total disrespect of our heritage. That’s a total disrespect of everything that we stand for,” Trump said, encouraging owners to act.

“Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, you’d say, ‘Get that son of a bitch off the field right now. Out! He’s fired,” Trump said to loud applause.

Trump also predicted that any owner who followed the presidential encouragement would become “the most popular person in this country” — at least for a week.

The players’ union said in a statement that “no man or woman should ever have to choose a job that forces them to surrender their rights. No worker nor any athlete, professional or not, should be forced to become less than human when it comes to protecting their basic health and safety.”

The NFLPA said “the line that marks the balance between the rights of every citizen in our great country gets crossed when someone is told to just ‘shut up and play.”’